JP3332612B2 - Brushless motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving device, and more particularly to a device for controlling the operation of a brushless motor based on a detected position of a rotor by induced voltage.

[0002]

2. Description of the Related Art Conventionally, a brushless motor has a rotor having a plurality of permanent magnets and a stator having a plurality of stator windings for generating a rotating magnetic field for rotating the rotor. The brushless motor driving device that controls the operation of the brushless motor detects the position of the rotor by comparing the induced voltage generated in the stator winding with the neutral point voltage in order to efficiently rotate the rotor, and for example, detects the rotation. There is a configuration in which the combination of stator windings to be energized is sequentially changed each time the child rotates 60 degrees.

FIG. 6 shows a waveform of an induced voltage of a stator winding in such operation control. In FIG. 6, commutation is performed every 60 degrees. This indicates that a spike voltage is generated from. When the induced voltage generated in the stator winding gradually increases and reaches the neutral point voltage, the position of the rotor is detected at this time, and a predetermined delay time T at which the electrical angle becomes 30 degrees thereafter. Indicate that commutation is performed and the combination of stator windings to be energized can be changed.

[0004]

By the way, in such a conventional brushless motor driving device, when the motor load increases, the spike voltage width H at the time of commutation increases, and the induced voltage and the neutral voltage at the end of the spike voltage are increased. The difference Vs from the point voltage (hereinafter referred to as a margin) decreases as shown in FIG.

If the margin Vs becomes small as described above, it becomes difficult to compare the induced voltage with the neutral point voltage, making accurate position detection operation difficult. If the motor load is further increased, the spike voltage width H becomes large. Is further increased, the margin Vs is lost, and the position detection itself may not be possible, and there is a problem that the reliability of the position detection operation is reduced.

In addition, immediately after the start of energization of the motor and until the steady operation, the rotor is rotating at a low speed, so that the induced voltage generated in the stator winding is small and the rotor speed is unstable. Often. Therefore, when the electric angle T as in the normal operation is set as the delay time, there is a problem that stable operation becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and enables accurate position detection irrespective of the motor load and stable position detection irrespective of the operation state of the brushless motor. It is an object of the present invention to provide a brushless motor driving device capable of driving.

[0008]

According to a first aspect of the present invention, there is provided a stator having a rotor having a plurality of permanent magnets and a plurality of stator windings for generating a rotating magnetic field for rotating the rotor. A brushless motor comprising: a plurality of stator windings; an inverter configured to sequentially change a combination of energization of the plurality of stator windings to generate the rotating magnetic field; and a rotating motor configured to rotate by the rotating magnetic field based on an induced voltage generated in the stator windings. Position detecting means for detecting the position of the rotor, and outputting an energizing switching signal for changing an energizing combination to the inverter based on a position detecting signal input from the position detecting means, A control device for outputting the signal after a predetermined delay time has elapsed from the detection time, wherein the control device outputs the delay time when the brushless motor commutates. Delay time changing means for changing in accordance with the voltage range of the microphone voltage are those which are provided.

According to a second aspect of the present invention, the control device further comprises: a rotation speed detecting means for detecting a rotation speed of the rotor based on the position detection signal; And a delay time changing means for changing the rotation speed in accordance with the rotation speed detected by the rotation speed detection means.

[0010]

[0011]

According to the first aspect of the present invention, a rotating magnetic field is generated by sequentially changing a combination of energizing a plurality of stator windings wound on a stator of a brushless motor by an inverter.
A rotor having a multi-pole permanent magnet is rotated. Further, the position of the rotating rotor is detected by the position detecting means based on the induced voltage generated in the stator winding. The control device that outputs an energization switching signal for changing the energization combination to the inverter outputs the energization switching signal based on the position detection signal input from the position detection means after a predetermined delay time has elapsed from the position detection time. To do. Further, a delay time changing means provided in the control device changes the delay time according to a voltage width of a spike voltage generated at the time of commutation of the brushless motor.

According to the second aspect of the present invention, the rotational speed of the rotor is detected by the rotational speed detecting means provided in the control device based on the position detection signal, and the delay time is changed by the delay time changing means to the voltage width of the spike voltage. And the rotation speed detected by the rotation speed detection means.

[0013]

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a brushless motor driving device according to the present invention.

In FIG. 1, 1 is a brushless motor (hereinafter referred to as a motor), 2 is an AC power supply, 3 is a rectifier circuit, and 4 is equipped with a plurality of switching elements. An inverter 5 for generating a rotating magnetic field for rotating the motor 5 is a current detector.

Reference numeral 6 denotes each fixed winding 7a, 7b, 7 of the motor 1.
c is a position detecting circuit which is a position detecting means for detecting the position of the stator rotating by the rotating magnetic field based on the induced voltage generated at the position c, and 8 based on the position of the stator detected by the position detecting circuit 6. This is a control device including a microcomputer having a rotation speed detecting means for outputting an energization switching signal to the inverter 4 so as to switch a combination of energization to the stator winding and detecting a rotation speed of the rotor.

The control device 8 compares the detected rotation speed of the rotor with a predetermined rotation speed Ns. If the detected rotation speed is lower than the predetermined rotation speed Ns, The motor 1 is determined to be in an operation state immediately after the start of energization to a steady operation, and the delay time is set to a delay time To shorter than that in the normal operation. On the other hand, when the detected rotation speed is higher than the predetermined rotation speed Ns, the motor 1 is determined to be in the steady operation state, and the delay time is set to the delay time T in the normal operation.

By setting the delay time To in the operation state from immediately after the start of energization to the steady operation as described above, the delay time is shorter than that in the normal operation, as shown in FIG. At this time, the energization switching can be switched earlier so as not to be delayed, whereby a stable position detection operation can be performed as in the steady operation.

The control device 8 measures a voltage width of a spike voltage of the motor 1 (hereinafter referred to as a spike voltage width), and controls the inverter 4 according to the spike voltage width.
And a delay time changing means for changing a delay time of the energization switching signal sequentially output to the control circuit.

Here, when the spike voltage width H is not equal to the predetermined voltage width Hs, the delay time changing means determines that the load of the motor 1 is a normal load and sets the delay time to, for example, an electric load. When the angle is set to 30 degrees and the spike voltage width H is a predetermined voltage width Hs,
The load of the motor 1 is determined to be overloaded, and the delay time is changed to a value smaller than that of the normal load, for example, to an electrical angle of 20 degrees.

When the load of the motor 1 is overloaded, the delay time is set to an electrical angle of 20 degrees, as shown in FIG. (See FIG. 7)
10) (P) in electrical angle as compared with the reference angle, and the margin Vs of position detection at the end of the spike voltage can be increased.

That is, when the spike voltage width H is smaller than the predetermined voltage width Hs (see FIG. 6), the spike voltage width H becomes the predetermined voltage as shown in FIG. When the width is larger than the width Hs, by increasing the margin of position detection, it is possible to change the delay time to a position in which reliable position detection is possible. As a result, accurate position detection can be performed without being affected by spike voltages generated during commutation.

Next, the operation control operation of the motor 1 configured as described above will be described with reference to the flowchart shown in FIG.

When the start switch is pressed and energization is started to start the motor 1, the control device 8 detects the position of the rotor with the position detection circuit 6 and the position detection circuit 6.
When a position detection signal is input from the controller (Y in decision 50), the rotation speed of the rotor is detected based on the detection signal, and whether the detected rotation speed has reached a predetermined rotation speed Ns is determined. A decision is made (decision 51).

The detected rotation speed is equal to a predetermined rotation speed N.
If s has not been reached (N in decision 51), it is determined that the motor 1 is in an operating state from immediately after the start of energization to a steady operation, and the delay time is compared with that in normal operation. A short delay time To is set (process 52). As a result, after the delay time To elapses from the detection of the rotor position (Y in decision 53), commutation is performed (process 54), and a stable position detection operation becomes possible as in the steady operation. . Such a position detection operation is performed while the motor 1 is operating (Y in the judgment 55).

On the other hand, while the operation of the motor 1 is continued, the position of the rotor is continuously detected by the position detection circuit 6 at a predetermined timing, and the rotation speed of the rotor is reduced to the predetermined rotation speed. It is determined whether or not the rotation speed has reached Ns (determination 51). When the detected rotation speed reaches a predetermined rotation speed Ns (Y in determination 51), the control device 8 determines that the spike voltage width H generated by the motor 1 has reached a predetermined value. It is determined whether the voltage width Hs has a predetermined magnitude (determination 56).

If the spike voltage width H is not equal to the predetermined voltage width Hs (N in decision 56), the load on the motor 1 is determined to be a normal load, and the delay time is set to the electrical angle. It is set to 30 degrees (process 57). After the elapse of the delay time set at the electrical angle of 30 degrees (Y in determination 53), commutation is performed (process 54), and steady operation is performed.

When the spike voltage width H is equal to the predetermined voltage width Hs (Y in decision 56), it is determined that the load of the motor 1 is overloaded, and the delay time is reduced. The electrical angle is set to 20 degrees smaller than the load (processing 5
8). After the elapse of the delay time set at the electrical angle of 20 degrees (Y in determination 53), commutation is performed (processing 54), and such steady operation is in operation (determination 55).
Y), which is subsequently performed.

As described above, by changing the delay time in accordance with the spike voltage width H generated at the time of commutation of the motor 1 and the number of rotations of the rotor, the delay time can be stabilized in accordance with the load and operating state of the motor. Position detection operation can be performed.

In the above description, the case where the delay time is changed in accordance with the spike voltage width has been described. However, the present invention is not limited to this. It may be changed according to the rotation speed of the rotor. That is, even if the spike voltage width H is small, the mode becomes the same as the case where the spike voltage width H is relatively large when the rotation speed is large, and the rotor speed is set to the number of rotations per second and the spike voltage. If the width is expressed as a time width, the relative spike voltage width H is expressed as an angle of 360 × N × H.

On the other hand, since the delay time is also expressed as an angle, the delay time is determined by comparing the voltage width expressed by these angles with the delay time, and the delay time is returned to the time unit for control. . Accordingly, when the relative spike voltage width is small, the delay time at the center of the efficiency can be set as the delay time, and when the relative spike voltage width is large, the delay time at which the position can be reliably detected can be set.

On the other hand, there are cases where the measurement of the spike voltage width cannot be performed due to various restrictions. In this case, the delay time is changed to the pulse width for adjusting the DC voltage applied to the motor 1 instead of the spike voltage width. It may be changed according to the duty ratio of the modulation and the rotor speed.

That is, considering that the duty ratio is large and the rotation speed is low, the load is large and the spike voltage width is large, and that the load is small and the spike voltage width is small if the duty ratio is small and the rotation speed is large. The relative spike voltage width is indirectly represented by the relationship between the duty ratio of pulse width modulation and the rotor speed to determine the delay time.

In this case, in order to determine the delay time, either one of the duty ratio or the rotation speed may be used, but it is more preferable to use both of them. The types are widened, and the delay time can be controlled more reliably.

In the above description, the delay time is set to two types, that is, the electric angle of 20 degrees and the electric angle of 30 degrees. However, the present invention is not limited to this, and the spike voltage width (or the relative speed between the rotor speed and the spike voltage) is not limited thereto. The relationship between the target spike voltage width and the delay time may be changed continuously as shown in FIG. In the figure, the upper limit of the delay time is represented by 30 electrical degrees, and the lower limit is represented by T1.

[0037]

As described above, according to the present invention, by changing the delay time in accordance with the voltage width of the spike voltage, accurate position detection independent of the spike voltage becomes possible. Further, when the spike voltage cannot be detected, by changing the delay time according to the duty ratio of the pulse width modulation and the rotor speed, accurate position detection not affected by the spike voltage can be performed. Further, by changing the delay time according to the rotation speed of the rotor, a stable position detection operation can be performed regardless of the operation state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a brushless motor driving device according to the present invention.

FIG. 2 is a diagram showing an induced voltage waveform from immediately after energization of a brushless motor of the driving device to a steady operation.

FIG. 3 is a diagram showing an induced voltage waveform of a stator winding in the driving device.

FIG. 4 is a flowchart showing an operation control operation of the brushless motor of the driving device.

FIG. 5 is a diagram showing a state where a delay time is continuously changed according to a spike voltage width.

FIG. 6 is a diagram showing an induced voltage waveform of a stator winding in a conventional driving device.

FIG. 7 is a diagram showing an induced voltage waveform when the motor of the conventional driving device is overloaded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brushless motor 4 Inverter 6 Position detection circuit 8 Controller H, Hs Spike voltage width To, T Delay time

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-178588 (JP, A) JP-A-6-165569 (JP, A) JP-A-4-2755091 (JP, A) JP-A-5-175 276786 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 6/12 H02P 6/16

Claims (2)

(57) [Claims] 1. A brushless motor comprising: a rotor having a plurality of permanent magnets; a stator having a plurality of stator windings for generating a rotating magnetic field for rotating the rotor; An inverter for generating the rotating magnetic field by sequentially changing the combination of energization to the stator winding, and a position for detecting a position of the rotor rotating by the rotating magnetic field based on an induced voltage generated in the stator winding. A control unit configured to output an energization switching signal for changing an energization combination to the inverter after a predetermined delay time has elapsed based on a position detection signal input from the position detection unit; The apparatus is provided with delay time changing means for changing the delay time according to a voltage width of a spike voltage generated at the time of commutation of the brushless motor. Brushless motor drive. 2. The control device according to claim 1, wherein the controller detects a rotation speed of the rotor based on the position detection signal, and determines the delay time by a voltage width of the spike voltage and the rotation speed detector. 2. The brushless motor driving device according to claim 1, further comprising delay time changing means for changing the rotation time according to the detected rotation speed.